JPH03295020A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve reproducing output, traveling durability, and preservability of the medium by incorporating a specified sulfoxide derv. into a magnetic layer or to the surface of the magnetic layer. CONSTITUTION:A sulfoxide derv. expressed by the formula is incorporated into the magnetic layer or to the surface of the magnetic layer. In the formula, R and R' are hydrocarbon radicals having 1 - 26 carbon atoms. By this method, the obtd. medium has stable traveling durability even when used under conditions of high temp. and high humidity, or low temp. and low humidity, and shows improvement in the reproducing characteristics and no deterioration in storage.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a magnetic recording medium in which a magnetic layer is provided on a non-magnetic support, and in particular to a magnetic recording medium that has excellent runnability and durability under a wide range of temperature and humidity conditions. It is related to.

(Prior Art) In magnetic recording media, there is an increasing demand for higher density recording, and it is known that one way to meet this demand is to smooth the surface of the magnetic layer.

Furthermore, ferromagnetic thin film magnetic recording media are also being developed as next-generation media.

However, in the above-mentioned media, if the surface of the magnetic layer is made smooth to improve the conversion characteristics, the friction coefficient of the contact between the magnetic layer and the device system increases while the magnetic recording medium is running, and as a result, it is difficult to use it for a short period of time. The magnetic layer of the magnetic recording medium is likely to be damaged or peeled off.

In order to deal with such problems, methods are known in which a lubricant is added to the magnetic coating liquid or a method is applied to the surface of the magnetic layer.

Conventional lubricants include mineral oil, silicone oil, higher alcohol, higher fatty acid, fatty acid ester, beef tallow, whale oil,
Animal oils such as whale oil or vegetable oils have been used.

When the amount of conventional lubricants listed above is small, increasing the amount of lubricant to enhance its lubrication effect weakens the mechanical strength of the magnetic coating, causing the magnetic layer to be scraped and scraped powder to contaminate the running path. Or, sufficient durability for still playback could not be obtained. In order to improve the durability of still regeneration, it is possible to use a mixture of a fatty acid ester such as butyl stearate and a fatty acid such as myristic acid, as disclosed in Japanese Patent Publication No. 2828367, Japanese Patent Publication No. 51-39081, etc. Are known. However, when these disclosed examples are used, there is a drawback that when the tape is run at high temperatures, friction increases and the running tension of the magnetic tape increases.

When fatty acids are used alone, they are effective in improving image quality, but in order to obtain lubricity, it is necessary to use large amounts, and in this case, the magnetic layer becomes soft and its mechanical strength decreases. However, there was a drawback that the durability of still playback deteriorated.

Furthermore, the combined use of fatty acids and fatty acid ester compounds described in Japanese Patent Publication No. 51-39081 results in good still durability and relatively low tension, but 8
Under high temperature conditions such as 5% RH (relative humidity), running tension increases.

In order to eliminate these drawbacks, Japanese Patent Application Laid-Open No. 56-80828
proposed the use of saturated or unsaturated fatty acids and aliphatic hydrocarbyl phosphates in the magnetic layer. This proposal states that it has excellent lubricity at room temperature and high temperature, and has good abrasion resistance and durability for still regeneration.

However, recently, as consumer-grade flexible disk drive devices for VTRs, personal computers, and word processors have become more popular and older, the conditions for using magnetic recording media have also changed, such as use at low temperatures and use at high temperatures. It's starting to look like this. Therefore, magnetic recording media must be stable so that their running durability does not change even under various expected conditions, but conventionally known lubricants are not sufficient for performance. There was a problem of deterioration.

In addition, as another measure to improve running durability,
A method of adding abrasives (hard particles) to the magnetic layer has been proposed and implemented, but when adding an abrasive to the magnetic layer for the purpose of improving the running durability of the magnetic layer, it is necessary to add a considerable amount of the abrasive. Unless it is added to the ft, the effect of the addition is difficult to appear, that is, it is ultimately difficult to obtain running durability without sacrificing the ft magnetic conversion characteristics and head abrasion properties.

Therefore, the present inventors conducted extensive research on a lubricant that would solve the above-mentioned problems with ferromagnetic powder-coated lubricants, and found that by retaining sulfoxide derivatives in the magnetic layer, excellent durability could not be achieved with conventional lubricants. The present inventors have discovered that it is possible to obtain good sexual and environmental adaptability, and have thus come up with the present invention.

(Objective of the Invention) An object of the present invention is to provide a magnetic recording medium which has improved reproduction output, runnability, durability, and storage stability over a wide range of temperature and humidity conditions, and particularly has an improved coefficient of friction at high temperatures.

(Structure of the Invention) That is, the above object of the present invention is to provide a magnetic recording medium having a magnetic layer provided on a non-magnetic support, characterized in that the magnetic layer contains a sulfoxide derivative represented by the following general formula on the magnetic layer or on the surface of the magnetic layer. magnetic recording media.

(General formula) R-3-R' 1 (wherein R is a hydrocarbon group having 10 to 26 carbon atoms, R' is a hydrocarbon group having 1 to 26 carbon atoms) More preferably, the above object of the present invention This can be achieved by a magnetic recording medium characterized in that the magnetic layer contains ferromagnetic powder and a binder, and at least one of the resins contained in the binder has a polar group. Further, the above object of the present invention can be achieved by a magnetic recording medium characterized in that the magnetic layer is a ferromagnetic metal thin film formed by oblique vapor deposition.

That is, in the present invention, when a sulfoxide derivative is contained in the magnetic layer or is present on the surface of the magnetic layer, stable running durability can be obtained even when used under harsh conditions such as high temperature, high temperature, low temperature and low humidity. Moreover, it does not deteriorate when stored.

The reason why the sulfoxide derivative of the present invention provides such effects is not clear, but it is thought to be due to the following reasons.

In other words, the sulfoxide group, which is a polar group of the compound of the present invention, has a structure similar to that of dimethyl sulfoxide (DMSO), which is an excellent solvent with good solubility for both inorganic and organic substances. It has high affinity with materials, improves the wettability of inorganic materials to binders, and can further improve dispersibility.

On the other hand, the sulfoxide group has a high affinity with the binder, which is an organic substance, so that the hydrocarbon groups of the hydrophobic chain on the surface of the magnetic layer are easily oriented toward the surface, and exhibits good lubrication performance. Furthermore, it has high solubility in solvents such as hexane and MEK, and when top coated, it can be applied uniformly to the surface of the metal material, and a uniform alignment film can be formed. On the other hand, in the case of sulfonic acid ester, since it is itself a strong acid, it corrodes the surface of metal materials. In the case of metal salts and ammonium salts of sulfonic acid, the salt dissociates over time and becomes an acid that corrodes metal materials.

Alternatively, because of its low solubility in solvents, it is difficult to apply it uniformly, making it impossible to form a uniform alignment film.

Further, the compound of the present invention exhibits remarkable effects particularly when a polar group-containing binder is used as a binder for a coated magnetic recording medium.

This is because the polar group of the compound of the present invention is easily soluble in the binder and has a very strong inclination with the polar group of the binder, so that the lubricating performance can be maintained due to its anchoring effect. This is thought to be because sulfonic acid esters strongly adsorb to the ferromagnetic powder and therefore do not come out to the surface, and sulfonic acid ester salts have low solvent solubility and crystals precipitate on the surface, resulting in poor slipperiness.

The sulfoxide derivatives used in the present invention will be explained in detail below.

(General formula) R-3-R' 1 (However, R is a hydrocarbon group having 10 to 26 carbon atoms R' is a hydrocarbon group having 1 to 26 carbon atoms) As the sulfoxide derivative of the present invention, R is 10 or more 26
Sulfoxide derivatives of the following hydrocarbon groups can be selected regardless of molecular weight, branched structure, unsaturated bond, and isomer structure, but preferably non-aromatic hydrocarbon groups (however, aralkyl groups, etc. are included), and straight-chain alkyl groups are particularly preferred.

In this case, if the number of carbon atoms is 9 or less or 27 or more, the hydrophobic chain is too short or too long, or even oriented, so that no lubricity is exhibited.

R' can be selected regardless of molecular weight, branched structure, unsaturated bond, or isomer structure as long as it is a sulfoxide derivative of 1 to 26 hydrocarbon groups, but preferably non-aromatic carbonized A hydrogen group (however, an aralkyl group is included), and a straight-chain alkyl group is particularly preferred. Among them, more preferably carbon number is 1 or more and 4
An alkyl group having an alkyl group of 10 or more and 26 or less is preferable from the viewpoint of highly densely oriented hydrophobic chains.

Specifically, CH3(CL) qs(Ijlz) lCH3 compound 1
1 CH3(C)12) Its(CH2)ZSCH:l
Compound 21 CH3(CHz)+tsclh 11 Compound 3 CHs(C1h>tss(C11z)tcHs1 Compound 4 CHs(CHz)+5S(C)It)+tCHs1 Compound 5 CHi(C1lz)+qS(CHz)icHs1 Compound 6 CH3CCHz)zsscH=cHcHz
Compound 81 CrF2 (CH2)zss-φ Compound 91 These compounds can be prepared by, for example, dissolving sulfide in a solvent (acetone, MEK, etc.) and adding an oxidizing agent (hydrogen peroxide, perbenzoic acid, ozone, chromic acid, hydroperoxide, NBS
(N-butylsuccinimide), etc.), and after removing the solvent, distillation under reduced pressure and recrystallization.

When added internally to the magnetic layer of a general coated magnetic recording medium, the appropriate amount is 0.1 to 8% by weight based on the ferromagnetic powder. When applying a top coat to the surface of the magnetic layer of a coated magnetic recording medium, a suitable amount is 2 to 50 .mu./bo.

If the amount used exceeds this range, the sulfoxide derivative on the surface will be excessive, which may cause problems such as sticking or moisture absorption. On the contrary, there are problems such as decreased durability.

If the amount used is below this range, the surface amount will be insufficient and no effect will be obtained.

In the present invention, other lubricants may be mixed.

Lubricants that can be used in combination include saturated and unsaturated fatty acids (myristic acid, stearic acid, oleic acid, etc.), metal soaps,
N-substituted/N-unsubstituted fatty acid amides, fatty acid esters (including various monoesters, sorbitan, glycerin, fatty acid esters of polyesters such as glycerin, esters of polybasic acids, etc.), ester compounds with ether bonds, higher aliphatic alcohols , monoalkyl phosphates, dialkyl phosphates, trialkyl phosphates, paraffins, silicone oils, animal and vegetable oils, mineral oils, higher aliphatic amines; inorganic fine powders such as graphite, silica, molybdenum disulfide, tungsten disulfide; polyethylene,
Resin fine powder such as polypropylene, polyvinyl chloride, ethylene-vinyl chloride copolymer, polytetrafluoroethylene; α-olefin polymer; unsaturated aliphatic hydrocarbon that is liquid at room temperature, unmodified or unmodified perfluoroalkyl Examples include polyether and fluorocarbons.

The preferred usage amount of these mixed lubricants varies depending on the mode of use, but is generally 1/1O to 2 times the usage amount of the sulfoxide derivative of the present invention.

In the present invention, methods for retaining the sulfoxide derivative in the magnetic layer include a method in which the sulfoxide derivative is contained in the magnetic layer, a method in which the surface is coated with a top coat (a method in which the material is dissolved in a solvent and applied or sprayed on the substrate, and then dried). There are methods of melting the material and applying it to the substrate, methods of immersing the substrate in a solution of the material dissolved in an organic solvent and adsorbing the material to the surface of the substrate, and methods such as using the Langmuir-Prodgett method.

As the ferromagnetic powder used in the present invention, ferromagnetic iron oxide powder, Co-doped ferromagnetic iron oxide powder, ferromagnetic chromium dioxide powder, ferromagnetic metal powder, ferromagnetic alloy powder, barium ferrite, etc. can be used.

Examples of ferromagnetic alloy powders include metal content of 75-t% or more, metal content of 80 wL% or more, or at least one magnetic metal or alloy (Fe, Co Ni Fe
-Co Fe-Ni Co-NiCo-Fe-Ni
etc.), and other components (
AI, Si, S, 5cTi V Cr Mn, C
u, Zn, Y, M.

Rh, Pd, Ag, Sn, Sb, B, Ba, Ta.

W, Re, Au, Hg, Pb, P, La, Ce.

Pr, Nd, Te, Bi, etc.) can be mentioned. Further, the ferromagnetic metal component may contain a small amount of water, hydroxide, or oxide.

Methods for producing these ferromagnetic powders are known, and the ferromagnetic powder used in the present invention can also be produced according to known methods.

The shape and size of the ferromagnetic powder are not particularly limited and can be widely used. The shape may be needle-like, rice-grain-like, spherical, cubic, plate-like, etc., but needle-like and plate-like shapes are preferred from the viewpoint of electromagnetic conversion characteristics. There are no particular restrictions on the crystallite size or non-surface area, but depending on the crystallite size. 400 Å or less, S BEτ 30
pH 1 surface treatment of ferromagnetic powder with preferably nf/g or higher can be used without particular restrictions (the surface may be treated with a substance containing elements such as titanium, silicon, aluminum, etc., or with a substance containing elements such as carboxylic acid, sulfonic acid, It may be treated with an organic compound such as an adsorptive compound having a nitrogen-containing heterocycle such as sulfuric acid ester, phosphonic acid, phosphoric acid ester, benzotriazole, etc. The preferred pH range is 5-10.

In the case of ferromagnetic iron oxide fine powder, it can be used without any particular restriction on the ratio of divalent iron/trivalent iron.

As the binder used in the present invention, known thermoplastic resins, thermosetting resins, radiation-curable resins, reactive resins, and mixtures thereof, which have been conventionally used as binders for magnetic recording media, can be used. can.

The above resin has a Tg of -40°C to 150°C and a weight average molecular weight of 10,000 to 300,000, preferably 10,000 to 100,000.

Examples of the thermoplastic resin include vinyl chloride/vinyl acetate copolymer, vinyl chloride, vinyl acetate and vinyl alcohol,
Copolymers with maleic acid and/or acrylic acid, vinyl copolymers such as vinyl chloride/vinylidene chloride copolymers, vinyl chloride/acrylonitrile copolymers, ethylene/vinyl acetate copolymers, nitrocellulose, cellulose acetate Propionate, cellulose derivatives such as cellulose acetate butyrate resin, acrylic resin,
Rubber resins such as polyvinyl acecool resin, polyvinyl butyral resin, polyester polyurethane resin, polyether polyurethane, polycarbonate polyurethane resin, polyester resin, polyether resin, polyamide resin, amino resin, styrene butadiene resin, butadiene acrylonitrile resin, silicone Examples include resins and fluorine-based fats.

Among these, vinyl chloride resin is preferred because it has high dispersibility of ferromagnetic fine powder.

The above thermosetting resins or reactive resins are those whose molecular weight becomes extremely large when heated, such as phenol resins, phenoxy resins, epoxy resins, curable polyurethane resins, urea resins, melamine resins, alkyd resins, silicone resins, and acrylic resins. system reaction resin, epoxy-polyamide resin, nitrocellulose melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, urea formaldehyde resin, low molecular weight glycol/
Included are high molecular weight diol/polyisocyanate mixtures, polyamine resins, and mixtures thereof.

The radiation-curable resin used is one in which a group having a carbon-carbon unsaturated bond is bonded to the thermoplastic resin as a radiation-curable functional group. Preferred functional groups include acryloyl and methacryloyl groups.

In the binder molecules listed above, polar groups (epoxy groups, CO
t M, OH, NR1, NRs X.

SOz M, O3O* M, POx M! ,0P03
Mx.

However, M is hydrogen, an alkali metal, or ammonium, and when there are multiple M's in one group, they may be different from each other, X represents a halogen ion, and R is hydrogen or an alkyl group). This is preferable in view of the dispersibility and durability of the ferromagnetic powder, and the effect of adding the sulfoxide derivative of the present invention will be noticeable. The content of polar groups is preferably in the range of 10-7 to 10-3 equivalents, more preferably 10-' to 10-4 equivalents, per gram of polymer.

If the polar group content is less than 10-7 equivalents, the amount of lubricant that interacts with it will be small, making it difficult to form a uniform alignment film and reducing the slipperiness; if it is more than 10-1 equivalents, the binding agent This is not preferable because it increases the viscosity and reduces the dispersibility.

The polymeric binders listed above may be used alone or in combination, and can be cured by adding a known incyanate-based crosslinking agent and/or a radiation-curable vinyl monomer.

As an isocyanate-based crosslinking agent, two isocyanate groups are used.
Polyisocyanate compounds having at least 100% polyisocyanate, such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate,
Isocyanates such as xylylene diisocyanate, naphthylene-1,5-diisocyanate, 0-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane diisocyanate, reaction products of these isocyanates and polyalcohols, and products produced by condensation of these isocyanates. Examples include polyisocyanates. These polyisocyanates are manufactured by Nippon Polyurethane Industries ■ Color Coronate L, Coronate HL, Coronate H, Coronate EH, Coronate 2014, Coronate 2030, Coronate 2031,
Coronate 2036, Coronate 3015, Coronate 3040, Coronate) 3041, Millionate MR, Millionate MTL, Daltosec 1350, Daltosec 2170, Daltosec 2280, Takenate D102, Takenate DIION, Takenate) D200, Takenate D202, Sumitomo Bayer From ■ , Sumidur N75, Desmodule from West German Bayer, Desmodule IL, Desmodule N1
Desmodur HL is commercially available from Dainippon Ink & Chemicals under trade names such as Burnock D850 and Parnock D802.

Radiation-curable vinyl monomers are compounds that can be polymerized by radiation irradiation and have one or more carbon-carbon unsaturated bonds in the molecule, such as (meth)acrylic esters, (meth)acrylamides, Examples include allyl compounds, vinyl ethers, vinyl esters, vinyl heterogeneous N compounds, N-vinyl compounds, styrene, (methaneacrylic acid, crotonic acid, itaconic acid, olefins, etc.).

Among these, diethylene glycol di(meth) having two or more (meth)acryloyl groups is preferable.
(meth)acrylates of polyethylene glycol such as acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, etc.
Acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyisocyanate and hydroxy(meth)acrylate
There are reactants with acrylate compounds, etc.

These crosslinking agents preferably comprise 5 to 45 wt% of the total binder containing crosslinking agents.

All the binders (including crosslinking) in the magnetic layer of the present invention
The content of ferromagnetic fine powder is 10 to 40 wt%, preferably 15 to 3 Qwt%.

If the blending ratio of the binder is more than the above range, the degree of filling of the ferromagnetic fine powder will be low and the electromagnetic conversion characteristics will be deteriorated, whereas if it is less than the above range, the running durability will be decreased.

Materials for the non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene 2.6 naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacerate; resins such as polycarbonate, polyimide, and polyamideimide. If necessary, it may be metallized with a metal such as aluminum, or may be a metal foil such as an aluminum whistle or stainless steel foil.

The form of the support may be tape, disk, film, sort, card, drum, etc., and various materials are selected depending on the form.

The thickness of the non-magnetic support is 3 to 100μ, preferably 3 to 20μ for magnetic tape, and 20 to 20μ for magnetic disk.
100μ is a commonly used range.

The magnetic layer of the magnetic recording medium of the present invention preferably further contains inorganic particles having a Mohs hardness of 5 or more as an abrasive.

The inorganic particles used are not particularly limited as long as they have a Mohs hardness of 5 or more. Examples of inorganic particles having a Mohs hardness of 5 or more include Adze3 (Mohs hardness 9), TiO (6), and T+Oz (6.5).

5ift (7), 5n02 (6.5).

Examples include Cr, O, (9), and α Few 03 (5.5), and these can be used alone or in combination.

Particularly preferred are inorganic particles having a Mohs hardness of 8 or more. When inorganic particles with a Mohs hardness lower than 5 are used, the inorganic particles tend to fall off from the magnetic layer and have almost no abrasive action on the head, resulting in head clogging and poor running durability. Become.

The content of the inorganic particles is usually in the range of 0.1 to 20 parts by weight, preferably in the range of 1 to 10 parts by weight, based on 100 parts by weight of the ferromagnetic powder.

In addition to the above-mentioned inorganic particles, the magnetic layer preferably contains carbon black (particularly one having an average particle size of 10 to 300 nm (nanometers + 10-" m )).

Next, an example of a method for manufacturing the magnetic recording medium of the present invention will be described.

First, a magnetic paint is prepared by kneading and dispersing ferromagnetic powder, a binder, and, if necessary, other fillers and additives in a solvent. As the solvent used during kneading, solvents commonly used for preparing magnetic paints can be used.

There is no particular restriction on the method of cross-talk, and the order of addition of each component can be set as appropriate.

For example, it is also possible to prepare lubricants, additives, and crosslinking agents dissolved in a solvent and add them to a ferromagnetic powder dispersion prepared with a solvent, binder, ferromagnetic powder, etc. immediately before coating. .

When preparing a magnetic paint, known additives such as dispersants, antistatic agents, lubricants, etc. can also be used.

Examples of dispersants include fatty acids having 12 to 22 carbon atoms, salts or esters thereof, compounds in which part or all of the hydrogen atoms of these compounds are replaced with fluorine atoms, amides of the above fatty acids, aliphatic amines, and higher alcohols. , polyalkylene oxide alkyl phosphate, alkyl phosphate, alkyl borate, sarcosinate i
, alkyl ether esters, trialkyl polyolefins, oxyquaternary ammonium salts and lecithin,
Known dispersants such as low molecular weight epoxy compounds can be used.

When using a dispersant, the ferromagnetic powder 1 usually used is
It is used in a range of 0.1 to 10 parts by weight per 00 parts by weight.

Examples of antistatic agents include conductive fine powders such as carbon black and carbon black graft polymers; natural surfactants such as saponins; nonionic surfactants such as alkylene ogicides, glycerin and glycidols; higher alkyls. Cationic surfactants such as amines, quaternary ammonium salts, salts of pyridine and other heterocyclic compounds, phosphoniums or sulfoniums;
Examples include anionic surfactants containing acidic groups such as carboxylic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric or phosphoric esters of amino alcohols. can. When using the above conductive fine powder as an antistatic agent, for example, 0.00 parts by weight per 100 parts by weight of ferromagnetic powder. 1~
It is used in a range of 10 parts by weight, and when a surfactant is used, it is also used in a range of 0.12 to 10 parts by weight.

Note that the above-mentioned additives such as dispersants, antistatic agents, and lubricants are not described with the strict limitation that they have only the above-mentioned effects; for example, the dispersant is used as a lubricant. Alternatively, it may act as an antistatic agent. Therefore, it goes without saying that the effects of the compounds exemplified by the above classifications are not limited to those described in the above classifications4, and when using substances that have multiple effects, the amounts added should be as follows: It is preferable to decide in consideration of its effects.

The magnetic paint thus prepared is applied onto the non-magnetic support described above. At this time, a plurality of magnetic paints may be applied sequentially or simultaneously in layers.

Coating can be performed directly onto the non-magnetic support, but it can also be applied onto the non-magnetic support via an intermediate layer such as an adhesive layer.

The intermediate layer herein refers to a layer of adhesive alone or a composite film layer formed by dispersing non-magnetic fine particles such as carbon in a binder.

The intermediate layer containing carbon black can be arbitrarily selected as a binder from among various binders used in magnetic layers. The particle size of carbon black is 10 to 50 nm (
The binder and carbon black preferably have a weight ratio of 100:10 to 100:150.The thickness of the intermediate layer is 0.1 to 2 μm in the case of a simple adhesive layer, and In the case of a composite layer containing magnetic powder, the thickness is preferably 0.5 to 4 μm.

In addition, the intermediate layer contains the same lubricant used for the magnetic layer.
Or a different lubricant may be added.

Details of the method of dispersing the above-mentioned ferromagnetic powder and binder and the method of coating it on a support are described in Japanese Patent Laid-Open Publications No. 54-46011 and No. 54-21805.

The thickness of the magnetic layer applied in this way is generally in the range of about 0.5 to 10 μm, usually 0.7 μm after drying.
It is applied so that the thickness is in the range of ~6.0 μm.

When a magnetic recording medium is used in the form of a tape, the magnetic layer coated on the non-magnetic support is usually subjected to a treatment for orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment, and then dried. On the other hand, in the case of a disk-shaped medium, a non-orientation treatment using a magnetic field is applied to remove the magnetic properties. Thereafter, the surface is smoothed if necessary, and then cured by heat curing and/or radiation irradiation if necessary, and then cut into a desired shape.

A known back layer may be provided on the side of the nonmagnetic support on which the magnetic layer is not provided.

In the present invention, oblique deposition is a method in which a vapor flow of a ferromagnetic metal material is made incident at a certain angle of incidence θ relative to the normal to the substrate surface to deposit a magnetic thin film on the substrate surface.

In the present invention, the angle of incidence is generally 45° to 90″.
″ is desirable, especially the incident angle θmax is 60° to 90＠,
The incident angle θmin is preferably 45° to 75°.

As the ferromagnetic metal thin film material used in the present invention, Fe
, Co5Ni or other metals, or Fe-Co, Fe-N
15Co-Ni, Fe-Co-Ni, Fe-Rh, Fe
-Cu, Co-Cu, C.

-Au, Co-Y, Co-La, Co-Pr, Co-G
d, Co-5m, Co-PL, Ni-Cu, Mn-B
i, Mn-5b, Mn-Al! ,,Fe-Cr,Co-
Cr, Ni-Cr, Fe-Co-Cr.

These are ferromagnetic alloys such as Ni-Co-Cr and Fe-Co-Ni-Cr. Particularly preferred is CO or Co75
It is an alloy that contains over 100%.

The total thickness of the laminated ferromagnetic metal thin film is generally about 0.02μ because it needs to be thick enough to provide sufficient output as a magnetic recording medium and thin enough to perform high-density recording.
m to 5.0 μm, preferably 0.05 μm to 2.0
It is μm. The thickness of each magnetic thin film may be designed to be equal, or the thickness may be ±50% of the thickness of the ferromagnetic metal thin film closest to the substrate.

The vapor deposition in the present invention refers to the above-mentioned US Pat. No. 334,263.
In addition to the usual vacuum deposition described in the specification etc. of No. 2,
It also includes a method in which a ferromagnetic metal thin film is formed on a supporting substrate in an atmosphere in which the mean free path of the generating molecules is large by ionizing or accelerating a vapor flow using an electric field, magnetic field, electron beam irradiation, etc. For example, JP-A-51-14
Field vapor deposition method as shown in specification No. 9008, Japanese Patent Publication No. 43-11525, Japanese Patent Publication No. 46-29484,
Special Publication No. 47-26579, Special Publication No. 4945439,
Ionization vapor deposition methods such as those disclosed in JP-A-49-33890, JP-A-49-34483, and JP-A-49-54235 can also be used in the present invention.

Substrates used in the ferromagnetic metal thin film of the present invention include polyethylene terephthalate, polyimide, polyamide, polyvinyl chloride, cellulose triacetate, polycarbonate,
A plastic base such as polyethylene naphthalate is preferred, and in particular, in the present invention, a flexible plastic base having a surface roughness (RA) of 0.012 μm or less is preferred. Here, the surface roughness (RA) is J.I.
The cutoff is 0.25 m+ with the center line average roughness shown in item 5 of S-BO601. Furthermore, an undercoat layer is provided on the plastic base, and its surface roughness (ra) is
) of 0.012 μm or less may be used as the substrate.

Furthermore, in the present invention, a nonmagnetic layer may be interposed between the laminated ferromagnetic metal thin films. Preferred materials for the nonmagnetic intermediate layer are Cr, Si, and Aj! , Mn, Bi, T
i, Sn, Pb, In-Zn.

This layer is made of Cu or nitride of these oxidized materials.

(Effects of the Invention) The present invention contains a sulfoxide derivative in the magnetic layer or on the surface of the magnetic layer, so that it can be used in coated magnetic recording media and ferromagnetic metal thin film media at low temperature and low humidity (5°C, 10% RH).
and exhibits a low coefficient of friction and excellent running performance under severe conditions of high temperature and high quality (45°C, 90% RH).
In addition, it exhibits a good reproduction output and can achieve both electromagnetic conversion characteristics and running performance. Further, in the case of a ferromagnetic metal thin film type medium, an excellent magnetic recording medium with particularly little rust can be obtained.

〔Example〕

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Note that "parts" in the examples indicate "parts by weight."

[Example 1] After cross-dispersing the following composition for 48 hours using a Nigu and a ball mill, 5 parts of polyisocyanate was added thereto, and after cross-dispersing for another hour, it was cross-dispersed using a filter having an average pore size of 1 μm. It was filtered and a magnetic paint was prepared. The obtained magnetic paint was applied onto the surface of a polyethylene terephthalate support having a thickness of 10 μm using a reverse roll so that the thickness after drying was 4.0 μm.

Magnetic paint composition Ferromagnetic alloy powder (composition: Fe94%, Zn.

4%, Ni 2%; electromagnetic crab 15000e; specific surface area 54 bo/g) 100 parts vinyl chloride/vinyl acetate/maleic anhydride copolymer (manufactured by Nippon Zeon ■ 400X110A polymerization degree 400)
(A) or vinyl chloride/vinyl acetate copolymer (degree of polymerization 400)
(B) 12 parts polyester polyurethane (weight average molecular weight 40,000, number average molecular weight 25,000, type and number of polar groups are listed in Table 1) (C) 5 parts coronate, 4 parts abrasive ( α-alumina, average particle size 0.3 μm) 5 parts Lubricant (listed in Table 1) 1 part oleic acid 1 part butyl stearate 2 parts carbon blank (average particle size 40 nm) 300 parts methyl ethyl ketone The magnetic support is oriented in a magnetic field with a 3000 Gauss magnet while the magnetic paint is not dry.
After further drying, the film was subjected to supercalender treatment, and the openings were then slit to produce an 8 m videotape.

[Example 2] A cobalt-nickel magnetic film (thickness: 150 nm) was obliquely deposited on a polyethylene terephthalate film having a thickness of 13 μm to prepare a raw material for a magnetic recording medium. An electron beam evaporation source was used as the evaporation source, and it was charged with a cobalt-nickel alloy (Co: 80wt%, Ni: 20%), and the incident angle was 50° in an oxygen stream in a vacuum of 5 x 10 Torr. Oblique evaporation was performed to obtain the desired temperature. Various materials dissolved in methyl ethyl ketone were coated on the magnetic metal i film of the obtained magnetic recording medium, and samples were prepared by drying and designated as sample numbers 24 to 39 (Table 2).

The videotape obtained in the above manner was filmed using V and TR (Fuji Photo Film ■: FUJ I
A MHz signal was recorded and played back. The relative playback output of the videotape was measured when the 7 MHz playback output recorded on the reference tape (Comparative Example 18) was set as OdB.

The obtained videotape and a stainless steel pole are brought into contact (wrapping angle 180°) with a tension (T) of 50g, and under this condition, the videotape is required to run at a speed of 3.3cm/S. The tension (T2) was measured. Based on this measured value, the friction coefficient μ of the videotape was determined using the following calculation formula.

(Listed in Tables 1 and 2) 〃=1/x -I n (Tz /TI') The friction coefficient test was performed at a, 5°C, 110% RH, and b, 45°C.
The test was carried out under two conditions: , and 90% RH.

In addition, in order to investigate the corrosion of the ferromagnetic powder on the tape, the tape was left in a thermostat for a week at temperatures ranging from 20°C to 40°C and humidity from 10% to 100%, and then observed under a microscope. The amounts were compared relative.

As is clear from the results in Table 1, all of the Examples using sulfoxide derivatives of the present invention had low coefficients of friction under both conditions a and b, indicating that the tape did not corrode.

On the other hand, when only a fatty acid or an ester is used without using the compound of the present invention, the regeneration output is low and the friction coefficient is large, especially at high temperatures (condition b). Furthermore, it can be seen that sulfonic acid has many problems such as severe corrosion of the tape.

From the results in Table 2, it can be seen that the amount of rust generated is significantly smaller than that of lubricants with acidic groups, and is at the same level as when no lubricant is used at all.

Claims (3)

[Claims] (1) A magnetic recording medium comprising a magnetic layer provided on a non-magnetic support, characterized in that the magnetic layer or the surface of the magnetic layer contains a sulfoxide derivative represented by the following general formula. (General formula) ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ (However, R represents a hydrocarbon group with 10 to 26 carbon atoms, and R' represents a hydrocarbon group with 1 to 26 carbon atoms.) (2) The magnetic layer includes a ferromagnetic powder and a binder, and at least one of the resins contained in the binder has a polar group. magnetic recording media. (3) The magnetic recording medium according to claim (1), wherein the magnetic layer is a ferromagnetic metal thin film formed by oblique vapor deposition.